Dynamical charges in oxides: recent advances Original Research Article

The dynamical charge of a given ion measures the dipole induced in the material when this ion is displaced. In many oxides these charges are much different from the formal ionic charges: for instance, the oxygen dynamical charge can be of the order of −8 unit charges in ferroelectrics. The mechanisms responsible for these “anomalous” values have been elucidated in the past few years. I present here some most recent results where a given oxide is investigated using different, and complementary, theoretical schemes, in order to provide lower and upper bounds for the theoretical prediction. As case studies, I address the ferroelectric oxide KNbO3 and the antiferromagnetic oxide MnO.